1. Field
The present invention relates to the field of treadmills used for standup exercise. More particularly, the present invention relates to the suspension by which the treadmill belt is supported to distribute and absorb the the shock of foot impact.
2. State of the Art
The benefits of regular exercise to improve overall health, appearance and longevity are well documented in the literature. For exercise enthusiasts the search continues for safe apparatus that provides lower body exercise without foot impact shock damage to the legs and leg joints.
A treadmill is an exercise device which permits walking or running by moving a continuous belt along the length of a chassis. The belt slides over a supporting deck with speed controlled by motor with appropriate controls or load resistance, as in the case of a manual treadmill. The belt is flexible and is unable to rigidly support the weight of the user. As the user walks or runs on the belt, the belt is pressed against the underlying supporting deck to provide mechanical support for the user body weight. The belt is generally non-extensible and typically made of reinforced flexible synthetic rubber like material.
Early treadmill designs used supporting decks that were rigidly attached to a framework without a means to absorb the shock of foot impact causing various injuries such as stone bruise or shin splints because of its hard unyielding surface. More recent treadmills use some form of belt support that includes shock absorption.
Lee in U.S. Pat. No. 4,938,473 and Walstead in U.S. Pat. No. 5,330,401 use belt suspension systems that include guided moving carriers that connect to the belt with springs or cable. Hayes in EPO Pat. No. 0196877 inserts a cushion material on top of a rigid deck to support the belt. Dunham in U.S. Pat. Nos. 4,974,831 and 5,184,988 shows a rigid deck pivotally supported at the rear and supported on the front end by shock absorber loaded levers. Parikh et al. in U.S. Pat. No. 5,649,882 uses a rigid deck with multiple spring support. However, the most popular approach is a rigid deck comprised of hardwood or composite material that is supported by elastomeric cushions.
Kirk in U.S. Pat. No. 5,542,892 shows a floating rigid deck with linear foam cushion under the deck. Skowronski et al. in U.S. Pat. No. 5,382,207 used a plurality of elastomeric cushions under the rigid deck including elliptical shaped cushions. Dalebout in U.S. Pat. No. 5,279,528 provides continuous foam cushion or adjustable air bladder under the rigid deck. Deckers et al. in U.S. Pat. No. 5,441,468 uses a rigid deck rigidly attached to the frame at the rear end and having elastomeric cushions at the other end and intermediate the deck. Rodden in U.S. Pat. Nos. 5,454,772 and 5,336,144 shows aperture shaped elastomeric cushions and guides to support a rigid deck.
All of the cushion deck prior art tends to use relatively heavy rigid decks that can move substantially vertical with very limited or no horizontal movement to absorb shock. The cushions return virtually all of the shock energy vertically back to the foot of the user to encourage stone bruise or shin splints over time to a lesser degree than a deck with no cushion support. There remains a need for a deck support system that better distributes the foot shock with minimal shock return to the foot to allow extended periods of exercise without shock related injuries.
Generally, treadmill support decks are rigid and linear. However, Sockwell in U.S. Pat. No. 5,709,632 shows a curved deck having the center of curvature above the deck wherein the deck is rigidly supported with stationary cross members. Skowronski et al. in U.S. Pat. No. 5,382,207 uses a crowned deck with the center of curvature below the deck wherein the rigid deck is secured by multiple elastomeric supports. Zaitsev in U.S. Pat. No. 5,391,129 shows a curved treadmill engaging the hands of a prone user as a swimming training device. There remains a need for a semi-rigid curved deck that has a suspension system that will allow the deck to deform with foot impact, both vertically and horizontally, and quickly disperse and absorb the shock before it is returned to the foot.